Physically accurate glass surface touching diffuse surface
If an object is diffuse it will be diffuse in glass same as in the air or in water. If you drop something diffuse into water it does not become reflective because water is reflective it stays diffuse unless there is some other material in between it and water like for example air bubbles stuck in surface imperfections, dirt or oil, or something else or if the materials react chemically. If the object is fully submerged in another material, the way it reflects light will not change. The type of light that can reach the object or the amount of it can change because of the material it is in, but not it's reflectivity. If there is no interface of two transparent materials there will not be any change in the direction light travels as well, so there is no need to do anything at all for it to be accurate if an opaque object is fully submerged in a transparent material. 

The first image is physically correct if there is nothing inbetween the object and the glass and if the object is diffuse. Volumetric effects should work correctly as well, since all that is needed to calculate them is the depth from the surface of the glass to the surface of the object.